Medical practice has generally considered the fields of radiology (which may including imaging modalities such as computer tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) and X-ray imaging) and endoscopy as separate specialties. While CT and MRI may be used to provide 3D anatomical information, image acquisition typically is not in real-time and analysis of the images is typically retrospective. Endoscopy typically provides only 2D superficial information, but in real-time, with colour, contrast and texture, which may be useful for providing diagnostic information. Conventionally, endoscopy is typically performed as a separate procedure that is only qualitatively connected to 3D imaging modalities such as CT and MRI. Any spatial correlation of the information is typically made qualitatively by the clinician through comparison of common anatomical features.
Methods have been developed to enable co-visualization of the 2D images with 3D anatomical information derived from 3D images. Such methods typically been developed in the field of surgical guidance.
The registration of 2D endoscopic images with volumetric imaging has been an area of exploration and development primarily in the context of surgical guidance1,2 and bronchoscope tracking for guiding biopsies.3 In these cases, the endoscopy may typically serve to extend the clinician's vision into luminal organs, with tracking relating the position of the “eyes” with respect to volumetric imaging. To date, the role of endoscopy in radiation therapy may be typically limited to clinical evaluation of the tumor prior to therapy and response evaluation following therapy. This evaluation, however, may be typically independent of any 3D volumetric information except for that provided by the clinician's association of anatomical landmarks in their notes. It has been suggested that quantitative registration of endoscopy with radiation planning CT may be used as an aid in contouring superficial lesions not typically visible in volumetric imaging.